switch over to SkVertices object, and stop using deprecated methods.

This allows Skia to remove
  SK_SUPPORT_LEGACY_CANVAS_VERTICES
  SK_SUPPORT_LEGACY_BITMAP_SETPIXELREF
  SK_SUPPORT_LEGACY_PIXELREFFACTORY

Test: Existing CTS cover these changes

Running CtsGraphicsTestCases, there were 6 failures w/ and w/o this CL.
None of the 6 seems related to this CL.

Change-Id: I724082357d9f6cb699770df3c0b9ef555b957697